I would call your title exaggerated yet accurate. It's the nature of a small group of people forming a Corporation; you get titles that sound big when they're really not, at least not yet. There's a huge difference between being a CTO of company with hundreds or thousands of employees vs being a CTO of a company with six employees.

Now I've never been a CTO at all, so I'm not trying to disparage you. I hope your company grows and you get the chance to grow into the title. Good luck!